I had a 4 core radiator put into my car last summer. Probably overkill, but it solved most of my overheating problems. Air movement throught a 4 core radiator is poor at idle, so I had to built a sheet metal shroud to help the airflow. I don't like the way the shroud looks, but it works for now. I am going to try a few other tricks, like moving the fan closer to the radiator to see if I can do away with the shroud. The local radiator shop put the quad core in for me and they simply used an off the shelf core. Cost me about $150 if I remember correctly. A 3 core radiator might actually be the best core in these cars with optimal airflow at idle and sufficient water cooling at speed.
But what the heck do I know?
Bill Lewis Series II (needing bumper rechroming)